Intrauterine-diagnosed fetal intracranial adamantinomatous craniopharyngioma: A case report with histopathological and molecular characterization.

Craniopharyngiomas are the most common non-neuroepithelial intracerebral neoplasms in children but rarely occur before birth, and are typically associated with a poor prognosis. We present the case of a 39-year-old woman with a spontaneously conceived singleton pregnancy. At 20 weeks of gestation, ultrasound detected a 44×25 mm heterogeneously hyperechogenic intracranial mass located at the base of the sphenoid bone, extending bilaterally. Due to the poor prognosis, legal pregnancy termination was performed, followed by fetal autopsy. The 20-week-old male fetus weighed 528g. External examination revealed only macrocephaly. Internal evaluation identified a yellowish, heterogeneous suprasellar mass. Histological analysis showed squamous epithelium with peripheral palisading, stellate reticulum, wet keratin, and calcifications-features consistent with adamantinomatous craniopharyngioma. Tumor cells were immunoreactive for high- and low- to intermediate molecular weight cytokeratins and SOX9, while no pituitary hormones or neuroendocrine markers were expressed. Next-generation sequencing of tumor tissue revealed a pathogenic somatic CTNNB1 mutation (c.121A>G, p.Thr41Ala), with no BRAF p.Val600Glu mutation and no germline variants detected. No extracranial abnormalities were observed. This case supports the inclusion of adamantinomatous craniopharyngioma in the differential diagnosis of congenital sellar and suprasellar masses despite its rarity. The identification of a somatic CTNNB1 mutation aligns with findings in postnatally diagnosed cases. Thorough histopathologic and molecular characterization is essential to guide prenatal counseling and improve management of affected fetuses and newborns.